Unleash Your Chemistry Potential with Comprehensive Class 9 Chapter 1 Notes: Long Question Answers
Welcome to the world of Chemistry! Understanding the fundamentals of this subject is crucial for students preparing for board exams as well as entry tests and competitive examinations. In this blog post, we will be exploring the first chapter of Chemistry: Fundamentals of Chemistry. We have carefully curated long and comprehensive answers to some of the most important topics related to this chapter, including the role of Alchemists in the history of chemistry, branches of chemistry, elements, compounds, and mixtures, relative atomic mass, atomic mass unit, average atomic mass, chemical species (ions, molecular ions, free radicals), and the classification of molecules. These notes are designed in a well-presented format and are self-explanatory, ensuring that students can easily grasp the concepts and score high marks in their exams. Get ready to dive into the exciting world of Chemistry!
For MCQs on Fundamentals of Chemistry Click Here
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| Notes on Chapter 1 Fundamentals of Chemistry for school level students From Notes Libray of H.E.S (Health, Education, and Skills) |
Write down the contributions of Muslim scientists.
Contributions of Alchemists
From 600AD to 1600AD
the period is generally known as the period of Alchemists. Following are
some of the Alchemists and their contributions to the field of chemistry.
1. Jabir-Ibn-e-Hayyan
Year of birth 721 AD
Year of death 803 AD
- He is generally known as the father of Chemistry.
- He was probably the first chemist who had an equipped chemical laboratory.
- He knew about many chemical procedures, for example, he described the method of production of white lead.
- He invented a chemical and experimental procedure for the preparation of Nitric acid (HNO3) and Hydrochloric acid (HCl).
- He described methods of fractional distillation and a method for the extraction of metals.
2. Muhammad Ibne-Zikriya Al-Razi
Year of birth 864 AD
Year of death 930 AD
- He was not only an Alchemist but was also a successful physician and philosopher.
- He was a skillful surgeon.
- He was the originator of dividing things into living and non-living.
- He wrote 26 books but the most famous book was Al-Asrar. In this book, he discussed the different processes of Chemistry.
- He prepared Alcohol by means of fermentation.
3. Al-Beruni
Year of birth 937 AD
Year of death 1048 AD
- He had sound knowledge of chemical procedures and chemical combinations.
- He determined the densities of different substances.
- He also made contributions in the field of Mathematics, Physics, Metaphysics, History, and Geography.
4. Ibne Sina
Year of birth 980 AD
Year of death 1037 AD
- He is generally known as the Aristotle of the Muslim world.
- He is famous for his contributions in the field of medicine, Mathematics, Astronomy, Medicinal chemistry, and Philosophy.
- He was probably the first scientist who rejected the idea that metals could be changed into Gold.
- His books were taught in Europe for centuries.
Write a detailed note on Branches of Chemistry.
Branches of Chemistry
The wide scope of Chemistry can be categorized in different areas; these areas are called branches of Chemistry.
Following are the main branches of Chemistry.
1. Physical Chemistry
That branch of chemistry that deals with the study of physical properties of a substance and its chemical composition is called Physical Chemistry.
2. Organic Chemistry
That branch of chemistry that deals with the study of Compounds of Carbon and Hydrogen called Hydrocarbons and their derivatives is called Organic chemistry.
3. Inorganic Chemistry
That branch of chemistry that deals with the study of Elements and Compounds other than Hydrocarbons is called Inorganic chemistry.
4. Analytical Chemistry
That branch of chemistry that deals with the study of qualitative and quantitative analysis of matter is called Analytical Chemistry.
The word qualitative means what kind of atoms or molecules are present in a compound. While quantitative means how many atoms or molecules are there in a compound?
5. Biochemistry
That branch of chemistry that deals with the study of the synthesis and decomposition of compounds and their reactions that take place in the body of living organisms such as animals and plants is called Biochemistry.
6. Nuclear Chemistry
That branch of chemistry that deals with the study of Changes that take place in the nuclei of an atom, properties of particles present in the nucleus, and emission or absorption of radiation is called nuclear chemistry.
7. Industrial Chemistry
That branch of chemistry that deals with the study of chemicals
and chemical procedures that are used in Industries for making different
industrial products such as cement, glass, rubber, fertilizers, medicines, etc.
is called Industrial chemistry.
8. Environmental Chemistry
That branch of chemistry that deals with the study of the Interaction of chemical substances with the environment and their impact on it, is called Environmental chemistry. Air and Water pollutions are the two main areas studied by environmental chemists.
Write a detailed note on Element.
Element
A pure substance that can’t be broken down into simpler substances by ordinary chemical or physical means is called an Element.
Following are the Characteristic properties of elements
- Elements are made up of small units called atoms.
- The smallest particle of an element that may or may not exist freely is called an atom.
- Atoms are the smallest particle of elements that can enter into a chemical reaction and characterize by unique numbers called atomic numbers.
- All the atoms of an element are chemically the same.
- There are approximately 118 elements known up till now. Which are divided as
Natural Elements 92
Artificial/ Manmade elements 26
Total Elements 118
- All the objects in the physical universe are made up of one or more elements.
Symbols of elements
In 1814, Berzelius suggested a system for representing elements with symbols. Elements are represented by short letters or letters called Symbols of elements.
In most cases, the first letter of an element is taken in capital letters as the symbol. In some cases, where the first letter has already been used, then the initial letters in capital together with a small letter from its name are used.
Some symbols are taken from English names while some are taken out from their old Latin names.
|
S.No |
Name of Elements |
Symbols (From English Names) |
Symbols (From Latin/Greek Names) |
|
1 |
Boron |
B |
---- |
|
2 |
Carbon |
C |
---- |
|
3 |
Calcium |
Ca |
---- |
|
4 |
Magnesium |
Mg |
---- |
|
5 |
Phosphorus |
P |
---- |
|
6 |
Sodium (Natrium) |
---- |
Na |
|
7 |
Iron (Ferrum) |
---- |
Fe |
|
8 |
Potassium (Kallium) |
---- |
K |
|
9 |
Mercury (Hydragyrum) |
---- |
Hg |
|
10 |
Tin (Stannum) |
---- |
Sn |
|
11 |
Antimony (Stibium) |
---- |
Sb |
|
12 |
Tungsten (Wolfram) |
---- |
W |
|
13 |
Lead (Plumbum) |
---- |
Pb |
|
14 |
Silver (Argentum) |
---- |
Ag |
|
15 |
Gold (Aurum) |
---- |
Au |
Examples of elements
Copper is used in wire, Neon gas is used in electric tube lights, Mercury is used in thermometers, Oxygen is used in air, etc.
Write a detailed note on the Compound.
Compound
A pure substance that is made up of the chemical combination of two or more two elements in the definite ratio by mass is called a Compound.
The following are the main points for describing the compounds
- A compound is formed only by the chemical combination of two or more elements e.g. Sodium Chloride (NaCl) is formed by Na and Cl by Ionic Bond.
- A compound can be decomposed by Chemical means only e.g. NaCl can be decomposed into Na+ and Cl- by a chemical process known as electrolysis.
- A process through which electric current is passed through molten salt is called electrolysis.
- Compounds always possess properties different from their parent atoms e.g. Na is metal and Cl is a gas while the Compound NaCl is solid.
- The atoms from which a compound is made are called the parent atoms of that compound.
- Elements of a compound
always combine in
fixed ratio by mass e.g. there will always be a ratio of 1:1 between Na and Cl in NaCl.
- The composition of a compound can be represented by its formula e.g. NaCl is the formula of Sodium Chloride, so its formula (NaCl) shows that it is composed of Na and Cl.
The formula is the collection of symbols of elements written in a specific way.
Examples of compounds and their uses
Water is used for various daily activities, sucrose (the chemical name of sugar) is a source of carbohydrates, ethyl alcohol is used in wine, ethylene glycol is used as antifreeze, etc are some of the common examples of compounds. Some other compounds and their formulas are given in the table.
|
S.No |
Common
Name |
Chemical
Name |
Formula
of Compounds |
|
1 |
Bleaching
powder |
Calcium
hypochlorite |
CaOCl2 |
|
2 |
Caustic
Soda |
Sodium
Hydroxide |
NaOH |
|
3 |
Chile saltpeter |
Sodium
Nitrate |
NaNO3 |
|
4 |
Limestone |
Calcium
Carbonate |
CaCO3 |
|
5 |
Sugar |
Sucrose |
C12H22O11 |
|
6 |
Sodium
bicarbonate |
Sodium
bicarbonate |
NaHCO3 |
|
7 |
Lime/
Quick lime |
Calcium
Oxide |
CaO |
|
8 |
Magnesia |
Magnesium
Oxide |
MgO |
|
9 |
Marsh gas |
Methane |
CH4 |
Write a detailed note on the mixture.
Mixture
The combination of two or more substances (elements or compounds) associated by weak forces rather than strong chemical bonds is called a mixture.
The following points are important to remember about mixtures.
- A mixture is formed only by the physical combination of two or more substances; it means that there is no involvement of a chemical bond.
- The constituents of a
mixture can also be separated by physical means only. For example, from the mixture of iron and sand, the constituents can
be separated by a magnet.
- The constituents of a mixture retain their characteristic properties. For example, in the mixture of iron and sand, they will have the same properties before and after mixing.
- The constituents of a mixture may combine in any ratio. For example, in the mixture of iron and sand, the constituents can combine in any ratio.
Types of mixture
Mixtures may be classified into the following two types.
1. Homogeneous mixture
That type of mixture in which the composition is uniform throughout the mixture is called a Homogeneous mixture.
Homogeneous mixtures are also called Solutions.
For example, 1) Mixture of table salt and water.
2) Mixture of ethyl alcohol and water.
2. Heterogeneous mixture
That type of mixture in which the composition is non-uniform throughout the mixture is called a Heterogeneous mixture.
For example, Concrete is a heterogeneous mixture of sand, rock, and cement. Heterogeneous mixtures are also called colloids or colloidal solutions.
Differentiate by giving examples between an element, a compound, and a mixture.
Differences between elements, compounds, and mixtures
|
Basis of distinction |
Elements |
Compounds |
Mixtures |
|
Definition |
A pure substance that can’t be
broken down into simpler substances by ordinary chemical or physical means is
called Element. |
A pure substance that is made up
of two or more two elements in a definite ratio by mass is called a Compound. |
The physical combination of two
or more substances rather than a strong chemical bond is called a mixture. |
|
Purity |
Elements are pure substances. |
Compounds are also pure
substances. |
Mixtures are not pure
substances. |
|
Formation |
Elements are made up of their own
atoms. |
The compound is formed only by the
chemical combination of two or more elements e.g Sodium Chloride (NaCl) is
formed from Sodium (Na) and Chlorine (Cl) by Ionic Bond |
Mixtures are formed by physical
combination only e.g. Salt and water can combine to form a mixture. |
|
Decomposition |
Elements can’t be broken down. |
Compounds can be broken down by
chemical means only e.g NaCl can be decomposed into Na+ and Cl-
by a chemical process known as electrolysis. |
Constituents of the mixture can be
separated by physical means e.g. from the mixture of Iron pieces and sand
particles the constituents can be separated by magnet. |
|
Representation |
Elements can be represented by
short names or abbreviations called Symbols. e.g. K is the symbol of Potassium
(Kallium). |
Compounds can be represented by
their formula, which is the collection of symbols of elements, e.g. the
formula of Calcium Carbide is CaC2. |
There is no specific way to
represent mixtures, because of their variable composition. |
|
Ratio
among the constituents |
|
In the compound, the constituents
always combine in a fixed ratio. |
In the mixture, the constituents
have a variable ratio. |
Write a note on following
i. Relative atomic mass ii. Atomic mass unit (amu)
iii. Average atomic mass
I. Relative atomic mass
The mass of an atom of an element relative to the mass of 1/12 the mass of C-12 is called relative atomic mass.
Explanation
The size of the atom ranges from 1.67x10-24 g to 4.0x10-22 g. These extremely small values are not only impossible to measure but are also impractical to work with. For this reason, scientists preferred to compare atomic masses with the standard mass of C-12.
ii. Atomic mass unit (amu)
1 mol of C-12 contains 〖6.023 x 10〗^23 atoms (Avogadro's Number)
1 atom of C-12= 12/〖6.023 x 10〗^23 =〖1.993 x 10〗^(-23) g
So, we can calculate
1 a.m.u=1/12 x 〖1.993 x 10〗^(-23)=1.67 x〖10〗^(-24) g=1.67 x 〖10〗^(-27) kg
iii. Average atomic mass
The weighted average of atomic masses of naturally occurring isotopes of an element is called Average atomic mass.
As most of the elements are found in two or more isotopic forms therefore we rarely found the atomic masses of the elements in exact whole numbers. So in this case we have to find out the average atomic mass of an element.
The following calculations show how to find out the average atomic mass of Chlorine.
Data Isotopes of Chlorine %age abundance in nature
Cl-35 75%
Cl-37 25%
Required Average atomic mass of Chlorine =?
Solution
The formula to find the average atomic mass is given as
Average atomic mass = ((1stisotopexits %age)+(2ndisotpexits %age)+⋯)/100
Putting the values from the data in the above formula, we have
The average atomic mass of Cl
= ((35 x 75)+(37 x 25))/100
= ((2625)+(925))/100
=3550/100
= 35.5 amu
So, the average atomic mass of Chlorine is 35.5 amu.
Define Chemical Species. Also, describe the classification of Chemical Species.
Chemical Species
An atom or group of atoms that take part in a chemical reaction is called a Chemical Species.
A chemical species may be a neutral particle or it may carry a charge.
Classification of Chemical Species
Chemical Species can be classified into the following three categories
A. Ions
The net charge formed by an atom after losing or gaining electron/electrons in bond formation is called Ion and the atom is said to be ionized.
Explanation
As we know that in an atom the number of Protons (p+) is always equal to the number of Electrons (e-) hence atom remains in balance before bond formation, but after the bond formation the balance between p+ and e- is destroyed and we say that an atom becomes a charged particle i.e ionized.
Ions can be either Cations (Positively charged) or Anions (Negatively charged), which are explained as
I. Cation
The positive charge formed on an atom after losing the valence electrons is called Cation and the atom is said to be cationized.
Explanation
Take the example of Sodium (Na) having 11 electrons and 11 protons before bond formation with Chlorine (Cl) in NaCl. When Na loses its valence electron it will have a positive charge, because the number of Protons (p+) will exceed the number of electrons (e-).
|
Before bond formation |
|
After bond formation (losing) |
||
|
No of electrons with Na |
-11 |
No of electrons with Na |
-10 |
|
|
No of protons with Na |
+11 |
No of Protons with Na |
+11 |
|
|
Net Charge |
0 |
Net Charge |
+1 |
|
|
Anion or Cation |
None |
Anion or Cation |
Cation |
|
|
Atom is in balance |
Balanced is destroyed |
|||
|
Atom |
Cation |
|
|
|
|
|
|
|
Mg Mg++
or Mg+2 +
2e- |
|
ii. Anion
The negative charge formed on an atom after gaining the electrons is called Anion and the atom is said to be anionized.
Explanation
Take the example of Chlorine (Cl) having 17 electrons and 17 protons before bond formation with Sodium (Na) in NaCl. When Cl gains one more electron it will have a negative charge, because the number of electrons (e-) will exceed the number of Protons (p+).
|
Before bond formation |
|
After bond formation
(gaining) |
||
|
No of electrons with Cl |
-17 |
No of electrons with Cl |
-18 |
|
|
No of protons with Cl |
+17 |
No of Protons with Cl |
+17 |
|
|
Net Charge |
0 |
Net Charge |
-1 |
|
|
Anion or Cation |
None |
Anion or Cation |
Anion |
|
|
Atom is in balance |
Balanced is destroyed |
|||
Atom | Anion |
| |
| |
O + 2e- O-- or O-2 | |
A group of atoms may also carry a positive or negative charge but they are not simple ions. For example, SO4-2(Sulphate ion), NO3-1(Nitrate ion), NH4+1(Ammonium ion) etc.
B. Molecular Ions
The net charge formed on a molecule after losing or gaining electron/electrons in bond formation is called Molecular Ion and the molecule is said to be ionized.
Explanation
Just like an atom molecules are also neutral particles and they become charged particles after the bond formation. Molecular Ions develop on molecules instead of atoms.
They can also be categorized as
a. Cationic Molecular Ions
The positively charged molecules are called as Cationic Molecular Ions.
For example CO+1,O2+1,CH4+1,N2+1,SO2+1 are Cationic Molecular Ions.
b. Anionic Molecular Ions
The Negatively charged molecules are called Anionic Molecular Ions.
For example, (HOCH2-CH2OH)-1 and (C2H5OH)-1 are Anionic Molecular Ions.
C. Free Radicals
The highly reactive species that are formed by the breaking of stable molecules in such a manner that the resulting species get separated with unpaired electrons are called Free Radicals.
Explanation
Consider the reaction of a Chlorine molecule (Cl2) with Methane (CH4) in the presence of diffused sunlight, following steps are involved from the formation of free radicals till the final product is formed.
Step#1 Formation of Chlorine free radicals
In this step, the Chlorine molecule is breakdown into Chlorine atoms with unpaired electrons
i.e Cl2 2Cl
The dot on the Chlorine atom represents a single unpaired electron and therefore is a free radical.
Step#2 Reaction of Cl with CH4
The Chlorine free radical is high reactive species therefore it will immediately react with CH4 and thus another free radical called Methyl free radical will be formed.
i.e CH4 + Cl CH3 + HCl
Step#3 Reaction of CH3 (free radical) with Cl2
The Methyl free radical is high reactive species therefore it will also immediately react with the Chlorine molecule (Cl2) and again Chlorine free radical will form along with the formation of Chloromethane(CH3Cl).
i.e CH3 + Cl2 CH3Cl + Cl
In this way, a chain of reaction of free radicals with stable molecule will be propagated until the final product is formed. Free radicals are formed in some particular reactions.
Define Molecule. Describe the classification of molecules with examples.
Molecule
The smallest particle of an element or compound which can exist as an independent distinguishable entity is called a molecule.
A molecule is formed by a chemical combination of atoms. It is the smallest unit of a substance. Molecules are the smallest particle of matter which can exist freely in nature. Examples of molecules are He, H2, NH3, H2SO4, CH4
Classification of Molecules
A. Classification on the number of atom basis
1. Monoatomic Molecules
Those molecules that are made up of only one atom are called monoatomic molecules.
For example, Helium (He), Neon (Ne), Argon (Ar) i.e. all the noble gases.
2. Polyatomic Molecules
Those molecules that are made up of more than one atom are called polyatomic molecules.
For example, Hydrogen molecule H2, Water, H2O, Ammonia NH3, Sulphuric Acid H2SO4, etc.
Polyatomic molecules are further subdivided into
I. Di-atomic molecules consist of two atoms e.g. H2, Cl2, CO, etc.
ii. Tri-atomic molecules consist of three atoms e.g. H2O, CO2, etc.
iii. Tetra-atomic molecules consist of four atoms e.g. NH3, CO3, etc.
iv. Penta-atomic molecules consist of five atoms e.g. CH4 etc.
Some molecules are made up of even thousands of atoms that are called Macromolecules (Marco=Very large). For example, the Haemoglobin molecule is made up of 10,000 atoms and is roughly 36,000 times heavier than ordinary Hydrogen.
B. Classification on the nature of atom basis
1. Homoatomic Molecules
Those molecules that are made up of the same atoms are called Homoatomic or Homonuclear molecules.
For example, O2, O3, S8, etc are Homoatomic in nature.
2. Heteroatomic Molecules
Those molecules that are made up of different atoms are called Heteroatomic or Heteronuclear molecules.
For example, HCl, H2SO4, NH3, H2O, etc
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